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* [tip: timers/core] posix-cpu-timers: Stop disabling timers on mt-exec
@ 2020-02-29 20:49 tip-bot2 for Eric W. Biederman
  0 siblings, 0 replies; 3+ messages in thread
From: tip-bot2 for Eric W. Biederman @ 2020-02-29 20:49 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: Eric W. Biederman, Thomas Gleixner, x86, LKML

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     d51692f23fc0249a9c4e32c81d32aef734a02daf
Gitweb:        https://git.kernel.org/tip/d51692f23fc0249a9c4e32c81d32aef734a02daf
Author:        Eric W. Biederman <ebiederm@xmission.com>
AuthorDate:    Fri, 28 Feb 2020 11:15:03 -06:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 29 Feb 2020 21:44:47 +01:00

posix-cpu-timers: Stop disabling timers on mt-exec

The reasons why the extra posix_cpu_timers_exit_group() invocation has been
added are not entirely clear from the commit message.  Today all that
posix_cpu_timers_exit_group() does is stop timers that are tracking the
task from firing.  Every other operation on those timers is still allowed.

The practical implication of this is posix_cpu_timer_del() which could
not get the siglock after the thread group leader has exited (because
sighand == NULL) would be able to run successfully because the timer
was already dequeued.

With that locking issue fixed there is no point in disabling all of the
timers.  So remove this ``tempoary'' hack.

Fixes: e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 kernel/exit.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 2833ffb..df54631 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -103,17 +103,8 @@ static void __exit_signal(struct task_struct *tsk)
 
 #ifdef CONFIG_POSIX_TIMERS
 	posix_cpu_timers_exit(tsk);
-	if (group_dead) {
+	if (group_dead)
 		posix_cpu_timers_exit_group(tsk);
-	} else {
-		/*
-		 * This can only happen if the caller is de_thread().
-		 * FIXME: this is the temporary hack, we should teach
-		 * posix-cpu-timers to handle this case correctly.
-		 */
-		if (unlikely(has_group_leader_pid(tsk)))
-			posix_cpu_timers_exit_group(tsk);
-	}
 #endif
 
 	if (group_dead) {

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* [PATCH 5/5] posix-cpu-timers: Stop disabling timers on mt-exec
@ 2020-02-28 17:15 Eric W. Biederman
  2020-03-01 10:27 ` [tip: timers/core] " tip-bot2 for Eric W. Biederman
  2020-03-04  8:57 ` tip-bot2 for Eric W. Biederman
  0 siblings, 2 replies; 3+ messages in thread
From: Eric W. Biederman @ 2020-02-28 17:15 UTC (permalink / raw)
  To: linux-kernel; +Cc: Oleg Nesterov, Thomas Gleixner


The reasons Oleg added the extra posix_cpu_timers_exit_group are not
entirely clear from his commit message.  Today all that
posix_cpu_timers_exit_group does is stop timers that are tracking the
task from firing.  Every other operation on those timers is still
allowed.

The practical implication of this is posix_cpu_timer_del which could
not get the siglock after the thread group leader has exited (because
sighand == NULL) would be able to run successfully because the timer
was already dequeued.

With that locking issue fixed there is no point in disabling all
of the timers.  So remove Oleg's ``tempoary'' hack.

Fixes: e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 kernel/exit.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 502b4995b688..c7f32101c2c8 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -103,17 +103,8 @@ static void __exit_signal(struct task_struct *tsk)
 
 #ifdef CONFIG_POSIX_TIMERS
 	posix_cpu_timers_exit(tsk);
-	if (group_dead) {
+	if (group_dead)
 		posix_cpu_timers_exit_group(tsk);
-	} else {
-		/*
-		 * This can only happen if the caller is de_thread().
-		 * FIXME: this is the temporary hack, we should teach
-		 * posix-cpu-timers to handle this case correctly.
-		 */
-		if (unlikely(has_group_leader_pid(tsk)))
-			posix_cpu_timers_exit_group(tsk);
-	}
 #endif
 
 	if (group_dead) {
-- 
2.25.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-03-04  8:57 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-02-29 20:49 [tip: timers/core] posix-cpu-timers: Stop disabling timers on mt-exec tip-bot2 for Eric W. Biederman
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2020-02-28 17:15 [PATCH 5/5] " Eric W. Biederman
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2020-03-04  8:57 ` tip-bot2 for Eric W. Biederman

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